Search

Abstract: Heavy neutrino with can be effectively searched for in kaon decays. We put upper limits on a mixing matrix element for radiatively decaying from decay chain in the following parameter region: ; . For the whole region for Majorana type of and for the Dirac case. [Copyright &y& Elsevier]

Abstract: The radiative decay has been studied at ISTRA+ setup in a new kinematic region. About 22K events of have been observed. The sign and value of have been measured for the first time. The result is . [Copyright &y& Elsevier]

Abstract: A search for the light pseudoscalar sgoldstino production in the three-body decay has been performed with the “ISTRA+” detector exposed to the negative secondary beam of the U-70 proton synchrotron. No signal is observed. An upper limit for the branching ratio , at 90% confidence level, is determined to be in the effective mass range from 0 to , excluding the region near where it degrades to . [Copyright &y& Elsevier]

The decay K-→π0e-ν is studied using in-flight decays detected with the “ISTRA+” spectrometer. About 920K events are collected for the analysis. The λ+ slope parameter of the decay form-factor f+(t) in the linear approximation (average slope) is measured: λ+lin=0.02774±0.00047(stat)±0.00032(syst). The quadratic contribution to the form-factor was estimated to be λ′+=0.00084±0.00027(stat)±0.00031(syst). The linear slope, which has a meaning of df+(t)/dt&z.sfnc;t=0 for this fit, is λ+=0.02324±0.00152(stat)±0.00032(syst). The limits on possible tensor and scalar couplings are derived: fT/f+(0)=-0.012±0.021(stat)±0.011(syst), fS/f+(0)=-0.0037+0.0066-0.0056(stat)±0.0041(syst). [Copyright &y& Elsevier]

The decay K−→π0μ−ν has been studied using in-flight decays detected with the “STRA+” spectrometer. About 540K events were collected for the analysis. The λ+ and λ0 slope parameters of the decay form-factors f+(t), f0(t) have been measured: λ+=0.0277±0.0013(stat)±0.0009(syst), λ0=0.0183±0.0011(stat)±0.0006(syst), and dλ0/dλ+=−0.348. The limits on the possible tensor and scalar couplings have been derived: fT/f+(0)=−0.0007±0.0071, fS/f+(0)=0.0017±0.0014. No visible non-linearity in the form-factors have been observed. [Copyright &y& Elsevier]

The decay K−→π0eν has been studied using in-flight decays detected with the “ISTRA+” spectrometer operating in the 25-GeV negative secondary beam of the U-70 PS. About 550K events were collected for the analysis. The λ+ parameter of the vector form-factor has been measured: λ+=0.0286±0.0008(stat)±0.0006(syst). The limits on the possible tensor and scalar couplings have been obtained: fT/f+(0)=0.021+0.064−0.075(stat)±0.026(syst); fS/f+(0)=0.002+0.020−0.022(stat)±0.003(syst). [Copyright &y& Elsevier]

The Dalitz plot slope parameters g, h and k for the K−→π0π0π− decay have been measured using in-flight decays detected with the ISTRA+ setup operating in the 25 GeV negative secondary beam of the U-70 PS. About 252 K events with four-momenta measured for the π− and four involved photons were used for the analysis. The values obtained g=0.627±0.004(stat)±0.010(syst), h=0.046±0.004(stat)±0.012(syst), k=0.001±0.001(stat)±0.002(syst) are consistent with the world averages dominated by K+ data, but have significantly smaller errors. [Copyright &y& Elsevier]

Results of the November 2000 test run of the prototype MVS system are described. The muon rejection factor at the level of 6.0×10−6 has been achieved with pion detection efficiency near 87%. [Copyright &y& Elsevier]